1. Field of the Invention
The present invention relates to a polycrystal for use in a solar cell, formed of a plurality of elements such as SiGe or InGaAs, and a method of manufacturing the same.
2. Description of the Related Art
As a method for manufacturing a polycrystal for use in a practical solar cell at low cost, a cast method (a kind of solidification method) is known. Although an Si polycrystal can be formed at low cost by the cast method, the Si polycrystal cannot absorb sunlight in a long-wavelength range of the solar spectrum. Due to this, the light conversion efficiency of the Si polycrystal is low. On the other hand, as a high efficiency solar cell, a tandem-form solar cell is known. The tandem-form solar cell has a hetero-structure having a thin-film compound-semiconductor stacked on a Ge or Si. However, the tandem-form solar cell has a problem in cost. Since it is formed by epitaxial growth, the cost is high.
As described above, a polycrystal for a solar cell providing high light-absorption efficiency at low cost has not yet been obtained. In fact, an appropriate polycrystal presently developed is chosen depending upon the use of the solar cell and put in use at present. However, recently, to use sunlight as a clean energy source more and more, the technique for developing a solar cell having a high conversion efficiency at low cost has been strongly desired.